Hydrodynamic behavior of a combined anaerobic-aerobic system employed in the treatment of vinasse

Abstract

The understanding of reactor hydrodynamics is essential for improving the performance of a reactor and biogas production. This study sought to evaluate the hydrodynamic behavior of a combined anaerobic-aerobic system at a laboratory scale for treating vinasse. The experiment was conducted in a system using two UASB reactors connected in series, followed by an Aerated Submerged Biological Filter (ASBF). The flow rates applied to the system and the corresponded theoretical HRTs in the UASB1, UASB2 and ASBF were respectively: 15.6 L d . The hydrodynamic studies were carried out using pulse type stimulus-response tests, employing LiCl as a tracer. The coefficients of determination for the dispersion models (R 2 ) indicate a close approximation of a continuous stirred tank reactor in series (multi-CSTR) model, with an average of 2.5, 2.3 and 1.2 (first year), and 1.1, 1.4 and 0.9 (second year) multi-CSTR for UASB1, UASB2 and ASBF, respectively. Results of the hydrodynamic tests carried out in UASB1, UASB2 and ASBF indicated strong tendency for flow in the complete mixture hydraulic regime, detecting a wide dispersion in the units, in addition to the presence of short circuits and dead zones.Index terms: Hydrodynamic study; tracers; biological treatment. RESUMOO entendimento sobre a hidrodinâmica dos reatores é essencial para melhorar o desempenho e produção de biogás destas unidades. O objetivo deste estudo foi avaliar o comportamento hidrodinâmico de um sistema combinado anaeróbio-aeróbio em escala laboratorial no tratamento da vinhaça. O experimento foi conduzido em um sistema utilizando dois reatores UASB em série seguidos por um biofiltro biológico aerado submerso (FBAS). As vazões aplicadas no sistema e os correspondentes TRHs teóricos nos reatores UASB1, UASB2 e FBAS foram respectivamente: 15,6 L d . Os perfis hidrodinâmicos foram realizados por meio de testes tipo pulso estímulo-resposta empregando como traçador LiCl. Os coeficientes de determinação (R 2 ) dos modelos de dispersão indicam uma maior aproximação do modelo de tanques de mistura completa em série (multi-CSTR), com uma média de 2,5; 2,3 e 1,2 (primeiro ano) e 1,1; 1,4 e 0,9 (segundo ano) reatores de mistura completa (multi-CSTR) em série para UASB1, UASB2 e FBAS, respectivamente. Os resultados realizados nos reatores UASB1, UASB2 e FBAS indicaram forte tendência do escoamento ao regime hidráulico de mistura completa, sendo detectada grande dispersão nas unidades, além da presença de curtos-circuitos e zonas mortas.Termos para indexação: Estudo hidrodinâmico; traçadores; tratamento biológico.

Impact of the Hydraulic Loading Rate on the Hydrodynamic Characteristics of an Anaerobic Fixed Bed Reactor Treating Cattle Slaughterhouse Wastewater

“…Greater oscillations in the tracer response occurred at an HRT of 14 h, which may be resulted from the internal recirculation of this tracer in the reactor. Fia et al (2016) also observed a delay in the response of the tracer, which may be linked to adsorption of the tracer by the biomass, or the existence of internal recirculation zones or dead zones inside the UASB reactors and ASBF, characterized by isolated or inaccessible regions where the imprisoned fluid does not interact with active regions.…”

“…It causes inversion of the gradient and diffusion begins to occur in the opposite direction. Fia et al (2016) and Zeng et al (2013) attributed this phenomenon to the tracer diffusion between the biofilm and substrate, considerable diffusion of the tracer into the biofilm, presence of dead zones or stagnation of the reactor, or eventually hydraulic short circuiting. Pérez-Pérez et al (2017) concluded that the presence of zeolite, used as material support in an expanded granular sludge bed (EGSB) reactor, caused higher values of dead zones, ranging from 12.3% to 24.2% and stated that the higher the zeolite bed the higher the percentage of dead zones in the EGSB reactor.…”